<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <script src="https://unpkg.com/vue/dist/vue.js"></script>
    <script src="https://unpkg.com/vue-router/dist/vue-router.js"></script>
    <title>p81使用watch监听文本框数据</title>
</head>
<body>
    <div id="app">
        <input type="text" v-model="firstname" >
        +
        <input type="text" v-model="lastname" >
        =
        <input type="text" v-model="fullname">
    </div>
    <script>
    var vm=new Vue({
        el:"#app",
        data:{
            firstname:"",
            lastname:"",
            fullname:""
        },
        methods:{
            
        },
        filters:{},
        directives:{},
        components:{},
        watch:{
            //使用这个属性，可以监视data中指定数据的变化，然后触发这个watch中对应的function处理函数
            firstname(newVal,oldVal){
                this.fullname=this.firstname+"-"+this.lastname
            },lastname(){
                this.fullname=this.firstname+"-"+this.lastname
            }
        }
    })
    </script>
</body>
</html>